The present invention relates to connectors for tubular members having either round or rectangular transverse cross-sections.
A variety of connectors are known for joining together tubular members having either a square or circular transverse cross-section. For example, if two tubular members are to be connected end to end, a cylindrical pin connector which extends into the adjacent ends of the tubes can be used. The tubes can be secured in place by means of set screws extending through the wall of each tube and into the pin connector. Similarly, it is possible to use a sleeve-type connector into which the ends of the tubes are inserted. However, such simple connectors are not suitable for connecting tubes or frame members together where members extend at an angle to one another or where a number of tubes or hollow frame members must be connected together at a single joint.
It will be appreciated that there are a number of uses for connectors which join tubular or hollow frame members together. Such connectors can be used in the construction of such things as furniture, playground equipment, display exhibits, sound and concert stages, elevated flooring, etc.
British patent application No. 2,006,379 published May 2, 1979, describes a connector for tubular members which employs an expandable spigot that is inserted in the end of the tubular member. The connector has a base which is fixedly connected to the support structure. The spigot has a pair of integral arms that extend from opposite edges of the base. The arms are formed with,inwardly directed, similar portions that are separated by a narrow slot. The tubular member is secured on the spigot by means of a screw with a pointed leading end. This screw cooperates with a corresponding tapped opening formed in the wall of the tubular member. By turning the screw, it enters the slot and expands the spigot into locking engagement. This connector can be made in one piece from metal such as aluminum or aluminum alloy.
International PCT patent application published under No. W093/19639 on Oct. 14, 1993, describes furniture made with a tubular underframe. Expandable assembly means are used to connect the legs and rails and to make up the rails. Each assembly device comprises two connecting members that are inserted in the end of the adjacent tube. One or more screws are passed through an opening in one of the connecting members and by turning this screw the connecting members are pressed against the inner side of the tube end. The pointed screw passes through an aperture formed in the side of the tube and the screw is threaded through a nut mounted in one of the two connecting members. The distal end of the screw pushes against a pressure plate mounted in the other connecting member. One difficulty with the assembly devices of this published international application is that they are not particularly suited for general use or for connecting a tubular member to a further tubular member extending at a right angle to the first tubular member and of similar size.